Roller Chain

ABSTRACT

In the case of a roller chain having pins, bushes, rollers, inner plates and outer plates, respectively two bushes are connected to each other by at least two inner plates and consequently form a chain link. A roller which surrounds each bush is mounted rotatably on the latter and respectively two successive chain links being connected to each other in an articulated manner in that each bush sits on one of the two ends of the bush protruding beyond the latter and two pins which are surrounded thus by two successive chain links are connected at least by two outer plates. The pins comprise austenitic stainless steel and their surface layer is formed by an S-phase of the austenitic steel which is obtained by nitriding.

The invention relates to a roller chain having pins, bushes, rollers, inner plates and outer plates according to the preamble of claim 1.

Chains of this type which are used frequently for drives are subjected to high wear and tear wherever surfaces are mounted to slide one upon the other, i.e. in particular on the insides of the bushes and abutting outer surfaces of the pins. In order to keep the wear and tear within limits, it is normal to provide good lubrication at the mentioned places. Inadequate lubrication leads however normally to rapid damage or destruction of the chain and in addition to drastic energy losses.

In order to reduce the susceptibility of generic chains to damage even in the case of inadequate lubrication, it is known according to prior art to coat the pins and/or the bushes with nitrides. However even these known chains have the disadvantage that the wear and tear which occurs during dry running of the chain with the lack of adequate lubrication at least on one of the two surfaces which slide respectively one upon the other exceeds the desired small value.

Furthermore, a high corrosion resistance of the chain parts is sought. This is provided with austenitic steels which are alloyed with chromium. However this material does not have adequate hardness to obtain the desired resistance to wear and tear. If the surface of the austenitic steel is hardened by one of the known nitriding methods, such as gas nitriding, plasma nitriding or impulse plasma nitriding, then an edge layer which contains a chromium nitride is formed, said edge layer indeed having the desired hardness and hence resistance to wear and tear but the corrosion resistance thereof having been considerably reduced.

It is therefore the object of the present invention to produce a roller chain having pins, bushes, rollers, inner plates and outer plates, in which respectively two bushes are connected to each other by at least two inner plates and consequently form a chain link, a roller which surrounds the bush being mounted rotatably on each bush and respectively two successive chain links being connected to each other in an articulated manner in that each bush sits on a pin which protrudes at both ends of the bush beyond the latter and two pins which are surrounded thus by two successive chain links are connected at least by two outer plates, in which roller chain in particular the pins have a surface not only of great hardness and hence with high resistance to wear and tear but also of high resistance to corrosion.

This object is achieved according to the invention by a roller chain having the features of claim 1. Advantageous developments of the roller chain according to the invention are revealed in the sub-claims.

As a result of the fact that the pins are made of austenitic stainless steel and their surface layer is formed by an S-phase of the austenitic steel which is obtained by nitriding, the edge layer of the pins contains no chromium nitride which reduces the corrosion resistance of the surface. The S-phase of the austenitic steel which is also termed “Expanded Austenite” represents a solid solution of nitrogen in the austenitic steel. The original austenite grating is widened by introducing the nitrogen.

The formation of chromium nitride takes place when the nitriding is effected at a temperature above 500° C. The normal nitriding methods operate in this temperature range since, at lower temperatures, the diffusion of nitrogen into the austenitic steel is extremely slow so that a process temperature of less than 400° C. which excludes the formation of chromium nitride is not justifiable from an economic point of view. An economically practicable route is however implantation of nitrogen which can be implemented at temperatures below 400° C. and with sufficient speed.

As a result of this nitriding process, the surface hardness can be raised for example from 400-500 HV to approx. 900-1000 HV, whilst the corrosion resistance of the austenitic steel is practically not impaired.

According to advantageous developments of the roller chain according to the invention, also the inner and outer plates and also the bushes can comprise austenitic stainless steel and their surface layer is formed by an S-phase of the austenitic steel which is obtained by nitriding. Consequently, a high resistance to wear and tear and also high corrosion resistance for all parts of the chain are obtained. The nitrided plate surface in addition increases the durability of the chain.

Furthermore, the bushes preferably comprise a sintered material which contains oil-filled pores. Hence a reliable and durable lubrication of the roller chain is ensured.

An embodiment of the invention is explained subsequently with reference to the FIGURE which shows a plan view, which is configured partially as a cross-sectional drawing, on a corresponding roller chain.

The roller chain depicted in the FIGURE comprises pins 1, bushes 2, rollers 3, inner plates 4 and outer plates 5. Respectively two bushes 2 are connected to each other by two inner plates 4 which are connected securely to these bushes 2 and form with these two inner plates 4 a chain link, a roller 3 which surrounds the bush 2 being mounted rotatably on each bush 2. Respectively two successive chain links of this type are consequently connected to each other in an articulated manner in that each bush 2 sits on a pin 1 which protrudes at the two ends of this bush 2 beyond the latter and two pins 1 which are surrounded thus by two successive chain links are connected by two outer plates 5, two ends of each pin being connected by respectively one outer plate 5. According to the invention, the pins 1 comprise austenitic stainless steel, their surface layer being formed by an S-phase of the austenitic steel which is obtained by nitriding. This applies preferably also to the bushes 2, which can be configured alternatively however also with a different hard coating, for example made of nitrides, formed in the conventional manner or DLC, a diamond-like carbon. The same applies to the rollers 3 and to the inner and outer plates 4, 5. 

1-4. (canceled)
 5. A roller chain, comprising: pins; bushes; rollers; inner plates; and outer plates, wherein in the outer plates, respectively two bushes of the bushes are connected to each other by at least two inner plates of the inner plates forming a chain link, wherein one of the rollers which surrounds one of the bushes is rotatably mounted on each bush and respectively two successive chain links are connected to each other in an articulated manner so that each bush sits on a corresponding pin which protrudes at both ends of the bush beyond the pin, two pins of the pins which are surrounded by two successive chain links being connected at least by two outer plates of the outer plates, and wherein the pins are made of austenitic stainless steel, a surface layer of the pins being formed by an S-phase of the austenitic steel which is obtained by nitriding.
 6. The roller chain according to claim 5, wherein the bushes comprise of a sintered material which contains oil-filled pores.
 7. The roller chain according to claim 5, wherein at least one of the inner plates and the outer plates comprises of austenitic stainless steel, a surface layer of at least one of the inner plates and the outer plates being formed by an S-phase of the austenitic steel which is obtained by nitriding.
 8. The roller chain according to claim 5, wherein the bushes comprise of austenitic stainless steel, a surface layer of the bushes being formed by an S-phase of the austenitic steel which is obtained by nitriding. 